#include "app_buffer.h"
#include <stdlib.h>
#include <string.h>
#include "log/log.h"

static SubBuffer *sub_buffer_init(int size){
    SubBuffer *sub_buffer = (SubBuffer *)malloc(sizeof(SubBuffer));
    sub_buffer->ptr = (char *)malloc(size);
    sub_buffer->size = size;
    sub_buffer->len = 0;

    return sub_buffer;
}
Buffer *app_buffer_Init(int size)
{
    Buffer *buffer = (Buffer *)malloc(sizeof(Buffer));
    buffer->sub_buffers[0] = sub_buffer_init(size);
    buffer->sub_buffers[1] = sub_buffer_init(size);
    buffer->read_index = 0;
    buffer->write_index = 1;

    //初始化读/写锁
    pthread_mutex_init(&buffer->read_lock,NULL);
    pthread_mutex_init(&buffer->write_lock,NULL);
    return buffer;
}

void app_buffer_free(Buffer *buffer)
{
    free(buffer->sub_buffers[0]->ptr);
    free(buffer->sub_buffers[1]->ptr);
    free(buffer->sub_buffers[0]);
    free(buffer->sub_buffers[1]);
    free(buffer);
}

int app_buffer_write(Buffer *buffer, char *data, int len)
{
    //得到写缓冲区
    SubBuffer *w_buffer = buffer->sub_buffers[buffer->write_index];
    //检查缓冲区是否还有足够的空间（容器本来的大小-已经存储的数据的长度=剩余可以存储的长度，）
    if (w_buffer->size-w_buffer->len < len + 1)
    {
        log_error("缓冲区");
        //解写锁
        pthread_mutex_unlock(&buffer->write_lock);
        return -1;
    }
    //先写入数据长度，再写入数据本身
    w_buffer->ptr[w_buffer->len] = len;
    memcpy(w_buffer->ptr+w_buffer->len +1,data,len);

    //更新len
    w_buffer->len += len + 1;
    //解写锁
    log_debug("写入数据后，解写锁");
    pthread_mutex_unlock(&buffer->write_lock);
    return 0;
}

static void sub_buffer_swap(Buffer *buffer){
    //加写锁
    log_debug("切换读/写缓冲区前，加写锁");

    pthread_mutex_lock(&buffer->write_lock);
    int temp = buffer->read_index;
    buffer->read_index = buffer->write_index;
    buffer->write_index = temp;
    //解写锁
    log_debug("切换读/写缓冲区后， 解写锁");
    pthread_mutex_unlock(&buffer->write_lock);
}
int app_buffer_read(Buffer *buffer, char *data_buf, int buf_size)
{
    //加读锁
    pthread_mutex_lock(&buffer->read_lock);
    //得到读缓冲区
    SubBuffer *r_buffer = buffer->sub_buffers[buffer->read_index];
    //如果读缓冲区为空，切换读/写缓冲区 如果还是空的，失败结束
    if (r_buffer->len == 0)
    {
        sub_buffer_swap(buffer);
        r_buffer = buffer->sub_buffers[buffer->read_index];
        if (r_buffer->len == 0)
        {
            log_error("读缓冲区为空");
            // 解读锁
            pthread_mutex_unlock(&buffer->read_lock);
            return -1;
        }
        
    }
    
    //读取数据长度(第一个字节数据) len
    int len = r_buffer->ptr[0];
    log_debug("读取数据长度:%d",len);
    //如果data_buf大小不够，失败结束
    if (buf_size < len)
    {
        log_error("data_buf大小不够");
        // 解读锁
        pthread_mutex_unlock(&buffer->read_lock);
        return -1;
    }
    //读取后面len个字节数据到data_buf中
    memcpy(data_buf,r_buffer->ptr+1,len);
    //将后面未读取的数据移到起始位置
    memmove(r_buffer->ptr,r_buffer->ptr+1+len,r_buffer->len-len-1);

    //更新读缓冲区的len
    r_buffer->len -= len + 1;

    //解读锁
    pthread_mutex_unlock(&buffer->read_lock);
    return len;
}
